Determination of the Optimal Impact Parameters for Microdissection of Zona Pellucida Using Femtosecond IR Laser Pulses

Dissection of mouse embryo zona pellucida was performed using femtosecond IR laser pulses (wavelength 1028 nm, pulse duration 280 fs, pulse repetition rate 2.5 kHz). The purpose was to investigate (using optical microscopy) the dependence of the width D of the cut formed by the laser beam on the laser pulse energy E and beam velocity υ. It was shown for the first time that the same value of cut width can be obtained at different combinations of the aforementioned parameters. An analytical expression is proposed to describe the dependence of the width of a cut made on a zona pellucida, D(E, υ), at a specified laser pulse repetition rate: 2.5 kHz. The applicability limits are found for the D(E, υ) functional, which set a wide range of laser beam velocities (0.25 µm/s ≤ υ ≤ 100 µm/s) and energies: from minimum values, corresponding to the cut formation onset, to the optical breakdown of the aqueous medium: 115 nJ ≤ E ≤ 190 nJ. The results obtained allow one to estimate rapidly the width of the planned cut for any combination of the parameters E and υ at microsurgery of embryo zona pellucida in the framework of various assisted reproductive technologies.